Volume 24 Number 9
Inorganic Chemistry
April 24, 1985
0 Copyright 1985 b y the American Chemical Society
Communications Correlations between Taft E , Parameters and 13C Chemical Shifts in Mo(CO),((Ph,PO),Si(Me)R) (R = Alkyl) Complexes. A New Method for the Measurement of Taft E , Parameters Sir: Complexes of the type Mo(CO),((Ph,PO),Y(R')R) (Y(R') = P(O), Si(Me); R = alkyl, haloalkyl, aryl) exhibit a number of unusual properties that make them useful for the study of the relationships between the steric and electron u-donor/?r-acceptor properties of phosphom-donor ligands and the multinuclear NMR spectra of their c o m p l e ~ e s . ' ~When R # R', two 13C NMR resonances are observed for the two carbonyl ligands cis to both of the diphenylphosphino groups and for the phenyl C( 1)'s of the two phenyl groups on the phosphorus.23 Good correlations between the chemical shifts of the trans-carbonyl 13C,cis and trans-carbonyl 1 7 0 and 31Presonances, and the averaged chemical shifts of the two cis-carbonyl and phenyl C(1) 13Cresonances are ~ b s e r v e d . ~ These good correlations suggest that changes in the steric effects of the Y(R)R' groups do not affect the averaged chemical shift values of these resonances since good correlations between the chemical shifts in question are not observed in similar Mo(CO),(Ph,PXR), (X = NH, 0, S; R = alkyl, aryl, silyl; n = 1 , 2 (cis)) complexes when changes in the steric properties of the XR groups do O C C U ~ . We ~ ~ ~now ~ ~ wish to report that the differences in the I3C chemical shifts of the two cis-carbonyl, phenyl C(1), phenyl C(2,6), phenyl C(3,5), and phenyl C(4) resonances of complexes of the type MO(CO),((P~,PO)~S~(M~)R) (R = alkyl, haloalkyl) are linearly related to the Taft steric parameters (E,) of the alkyl groups. This is one of the first cases in which NMR spectroscopy can be used to measure variations in both the steric and electron a-donor/?r-acceptor properties of a phosphorus-donor ligand. More importantly, this provides a relatively simple method for the measurement of the Taft steric parameters in an organometallic system. The 13C(1HJN M R data for the carbonyl and phenyl groups of the Mo(CO),((Ph,PO),Si(Me)R) complexes are summarized in Table I. The 13C resonances of the trans- and cis-carbonyl carbons, the phenyl C( 1)'s, and the remaining phenyl carbons of Mo(CO),((Ph,PO)Si(Me)c-Hx)are shown in Figures 1-3, respectively. As can be seen in these figures, two resonances are observed for the cis-carbonyl and phenyl carbons when R # Me. The trans carbonyls are symmetry related by a mirror plane that contains the methyl and R groups and thus remains equivalent regardless of the R group used. The trans-carbonyl and phenyl C(1), C(2,6), and C(3,5) 13Cresonances are apparent triplets or (1) (2) (3) (4) (5) (6) (7)
Gray, G. M.; Kraihanzel, C. S.J. Organomet. Chem. 1978, 146, 23. Gray, G. M.; Kraihanzcl, C. S . J. Organomet. Chem. 1982, 238, 209. Gray, G. M.; Kraihanzel, C. S.J. Organomet. Chem. 1983,241, 201. Gray, G. M.; Redmill, K. A. J . Organomet. Chem. 1985, 280, 105. Gray, G. M.; Kraihanzel, C. S.Inorg. Chem. 1983, 22, 2959. Gray, G. M. Imrg. Chim. Acta 198481, 157. Gray, G. M.; Gray, R. J.; Berndt, D. C. J . Magn. Reson. 1984,57,347.
0020-1669/85/1324-1279$OlSO/O
trans
I
I
"
'
216
l
"
'
l
I
214
212
'
'
I
zoa
210
'
PPM
Figure 1. 13C(1HJNMR spectrum of the cis- and trans-CO ligands of
Mo(C0)4((Ph2PO)2Si(Me)c-Hx).
l 144
'
o
"
'
I ' ' " 143 5
/
"
' 143
'
/
a
/ 142 5
'
'
' I ' " 142 o
'
I r 141 5
PPM
Figure 2. I3C('HJ NMR spectrum of the phenyl C ( l ) carbons of Mo(CO),( (Ph20)lSi(Me)c-Hx).
apparent pentets (the A portion of an AXX' spin system) due to coupling to magnetically inequivalent phosphorus nuclei.**9 The cis-carbonyl 13Cresonance is a 1:2:1 triplet (the A portion of an AX, spin system) since the phosphorus nuclei are symmetry related by a mirror plane that contains the cis carbonyls. The C(4)'s of (8) Redfield, D. A.; Nelson, J. H.; Cary, L. W. Inorg. Nucl. Chem. Lett. 1974, 10, 727. (9) Redfield, D. A.; Cary, L. W.; Nelson, J. H.Inorg. Chem. 1975, 14, SO.
0 1985 American Chemical Society
1280 Inorganic Chemistry, Vol. 24, No. 9, 1985
Communications
Table 1. I3C NMR Data for the Mo(CO),((PPh,O),Si(Me)R) Compoundsa carbonyl
phenyl
trans
cis
6
IIJ(PC) + J(P'C) I
Et (2)
21 4.94 214.94
18.2 17.9
CH,Cl (3)
214.43
18.6
n-Pr (4)
214.95
18.3
C-HX(5)
214.97
18.2
t-Bu ( 6 )
214.88
18.1
Ph (7)
214.83
18.8
R Me (1)
a J values are in
C(1)
6
12J(PC)I
6
208.57 208.41 208.72 208.30 208.43 208.34 208.84 207.98 209.17 207.56 209.43 207.55 209.28
10.6 10.8 10.9 10.8 10.9 10.7 10.6 10.6 10.6 10.6 10.5 10.3 10.7
142.42 142.48 142.60 141.86 142.01 142.41 142.69 142.34 142.94 142.31 143.09 142.16 142.58
19.0 18.5 19.1 19.2 19.0 18.2 18.9 18.1 19.7 17.6 20.0 18.4 19.5
levelof signif
C(3,5)
6
12J(PC)+ 4J(P'C) I
129.24 129.23 129.33 129.24 129.29 129.24 129.43 129.14 129.61 128.96 129.66 129.21 129.71
15.0 14.9 14.9 15.6 15.2 14.9 14.9 14.9 15.2 14.7 15.2 14.5 15.0
13J(PC)+ 'J(PC) +
C(4)
6
128.20 128.19
9.7 7.1
128.30
9.5
128.17 128.21 128.15 128.22 128.17 128.26 128.22 128.29
8.5 8.9 11.2 9.8 9.8 9.6 11.6 9.9
129.92 129.91 129.94 130.17 130.20 129.88 129.98 129.80 130.05 129.75 130.13 129.81 130.18
6
Hz.
Table 11. Coefficients (r) Calculated for the Linear Correlations between the E, Parameters of the R Groups and the Differences in the ''C Chemical Shifts of the Cis-Carbonyl and Phenyl Resonances of the Mo(CO),((Ph, PO),Si(Me)R) Complexes
r
C(2,6)
IIJ(PC) + 3J(P'C) I
cis CO
Ph C(1) PhC(2,6) PhC(3,5)
Ph C(4)
-0.978 99.9
-0.981 99.9
-0.984 99.9
-0.982 99.9
-0.936 99.0
2.0
-
1.5
-
2
1.0
.
6
0.5
I....
-
1
-2
0
\ c
-1.5
-1.0
-0.5
0.0
Es
Figure 4. Plot of the differences in the "C chemical shifts of the ciscarbonyl and phenyl carbons vs. the E, parameters of the alkyl groups in the Mo(CO),((Ph,PO),Si(Me)R) (R = alkyl) complexes.
the phenyl rings do not couple to either of the phosphorus nuclei and give rise to singlets. All 13CN M R spectra were obtained on a Nicolet 300-MHz N M R spectrometer under experimental conditions that have previously been reportedS4 A plot of the differences between the chemical shifts of the two resonances of the cis-carbonyl and phenyl carbons vs. the Taft E, parameterslo of the alkyl and haloalkyl groups of the Mo(CO),(PPh,O),Si(Me)R) complexes is given in Figure 4. As is evident from this figure, all the chemical shift differences increase with increasing IEJ. The coefficients ( r ) calculated for these correlations and the levels of significance of the correlations are given in Table 11. The lower correlation coefficient and level of significance of the correlation between the chemical shift differences of the phenyl C(3,5)'s and the E, parameters are a result of the small size of the chemical shift differences being measured (0.09 ppm maximum) relative to the data point reso-
lution of the experiment (f0.016 ppm). The correlations are significant for two reasons. The first is that these complexes are among the first reported in which it is possible to use N M R spectroscopy to measure simultaneous changes in both steric and electronic effects. This suggests that (Ph,PO),Y(R')R ligands could be useful in multinuclear N M R studies of the relationship between the steric and electron a-donor/wacceptor properties of these phosphorus-donor ligands and the catalytic activity and selectivity of their transition-metal complexes. Secondly, the correlations allow the Taft E, parameters to be easily measured as these complexes are readily synthesized from [Et,NH] [Mo(CO),((Ph,PO),H)] and the appropriate dichloro~i1ane.I.~Since a variety of dichlorosilanes are commercially available, a number of Es parameters can be measured and compared with those obtained from other sources.11 More importantly, this method allows the E, parameter to be measured at several different sites within the complex. If a constant value is obtained, the effect can be safely assumed to be a steric effect as is the case for the alkyl and haloalkyl complexes. However, if the value varies when measured at the different sites, this indicates that through-space diamagnetic anisotropic shielding or deshielding may be occurring since this should not be constant at all five sites. This is illustrated by the 13C N M R data for Mo(CO),((Ph,PO),Si(Me)Ph),which are included in Table I. The E, parameters for the Ph group calculated with the corre-
(10) Taft, R. w., Jr. "Steric Effects in Organic Chemistry"; Newman, M. S., Ed.;Wiley: New York, 1956; p 598.
(1 1) Gallo, R.'Progress in Physical Organic Chemistry"; Taft, R.W., Jr., Ed.;Interscience: New York, 1983; Vol. 14, pp 115-163.
130 0
129 5
123 5
128
5
ma o
PPM
F i e 3. 13C(1HJ NMR spectrum of the.phenyl C(2,6), C(3,5), and C(4) carbons of MO(CO)~((P~,O)~S~(M~)C-HX).
Inorg. Chem. 198;5, 24, 1281-1283 lations with the cis-carbonyl, phenyl C( l ) , phenyl C(2,6), phenyl C(3,5), and phenyl C(4) data are respectively -1.33, -0.70, -1.01, -1.00, and -1.53. The variation in these numbers is considerably greater than the error of the calculations, and these values are also considerably different from the E, parameter of -0.90, which has been reported for the phenyl group.'O Thus, this method allows for the separation of steric from electronic effects by multiple measurement of the E, parameter. Since this method appears to be extremely useful for the measurement of E, parameters, this study is currently being extended to determine the limits of the method. Included in this study are complexes in which the R group is a long-chain alkyl group or a polyhaloalkyl group and complexes in which the diphenylphosphino group is replaced by a 1,3,2-dioxaphosphorinane group. The results of this research will be reported in a subsequent communication. Acknowledgment. We wish to thank J. T. Baker Chemical Co. and the University of Alabama at Birmingham for supporting this research. Department of Chemistry University of Alabama at Birmingham Birmingham, Alabama 35294
Gary M. Gray* Keith A. Redmill
Received November 14, 1984
A Polymeric Peroxo Heteroligand Vanadate(V). Synthesis, Spectra, and Structure of M'[VO(O*) (Csr,O" Sir:
Vanadium peroxo complexes are known to act as catalysts',2 and have been proposed as one of the model systems for the biochemistry of v a n a d i ~ m . ~Although ?~ recently recognized as an essential element for mammals? the vanadium function remains unkn0wn.4~ Some of the peroxo heteroligand vanadates(V) have shown antitumor activity against L1210 murine leukemia, and the biological activity of these complexes4 strongly depends upon the heteroligands. We have been interested in the peroxovanadates(V) befores and have now decided to investigate such complexes containing amino carboxylato or polycarboxylato ligands, to find out some general trends regarding the influence of the heteroligand on the mode of coordination, the bond distances and the bond angles, the charge-transfer bands, the stability, and the reactivity of coordinated peroxides. We report now our work with the iminodiacetic acid, C4H7N04, which reacts with V(V) in the presence of hydrogen peroxide to form crystalline compoundsg of the formula M1[V0(O2)IDA] MI = K, NH,; IDA = [C4H5NO4I2-). Unlike other analogous oxo peroxo heteroligand vanadatessJO these complexes crystallize (1) Mimoun, H.; Saussine, L.;Daire, E.; Postal, M.; Fischer, J.; Weiss, R. J . Am. Chem. Soc. 1983, 105, 3101. (2) Patai, S. 'The Chemistry of Peroxides"; Wiley: New York, 1983. (3) Djordjevic, C.; Craig, S. A.; Lee, M. 186th National Meeting of the American Chemical Society, Washington, D.C., 1983. (4) Djordjevic, C.; Wampler, G. L. J. Inorg. Biochem., in press. ( 5 ) Mertz, W. Science (Washington, D.C.) 1981, 213, 1332. (6) Chasteen, N. D. Struct. Bonding (Berlin) 1983, 53, 105. (7) Kustin, K.; Macara, I. G. Comments Inorg. Chem. 1982, 2, 1. (8) Vuletic, N.; Djordjevic, C. J. Chem. SOC.,Dalton Trans. 1973, 1137. (9) Anal. Calcd for NH4[V0(02)IDA]: C, 19.4; H, 3.7; N, 11.3; 022-, 12.9; V, 20.5. Found C, 19.6; H, 3.7; N, 11.3; O?-, 12.2; V, 20.5. Calcd for K[VO(OJIDA]: C, 17.9; H,1.9; N, 5.2; OZ2-,11.9; K, 14.5; V, 18.9. Found: C, 17.9; H, 1.9; N, 5.2; OZ2-,12.5; K, 14.9; V, 19.4. (10) Djordjevic, C.; Lee, M.; Vuletic, N.; Craig, S. A. XXIII International Conference on Coordination Chemistry, Boulder, CO, 1984; p 31.
0020-1669/85/ 1324-1281$01.50/0
1281
anhydrous from the aqueous solutions and are remarkably stable toward decomposition. Aqueous solutions of the compounds show a band centered a t 420 nm, as observed for some other monoperoxovanadates.ll This absorption remains constant over a wide p H range of 2-8 but shifts a t pH I 1 to 450-460 nm, and a new band appears at 280 nm. In such acid solutions the complexes obviously rearrange, but the peroxo group remains coordinated to the In aqueous solutions the potassium and the ammonium complexes show identical cyclic voltammograms with characteristic irreversible cathodic and anodic peaks. Study of the electrochemical behavior of these complexes is in progress. The ammonium complex has shown marginal antitumor activity against L1210 murine l e ~ k e m i a . ~ The significant features in the IR spectra of the potassium and the ammonium compounds involve bands of coordinated IDA, peroxo frequencies, and V = O stretchings. The N H stretchings of the three-coordinated ligand shift to higher energy, and a sharp strong band occurs at 3215 cm-' as compared to strong absorption found at 3100 cm-' in the acid. The coordinated carboxylato groups cause a distinct shift of antisymmetric CO ~tretchings,'~ which occur as strong bands at 1680 to 1660 and 1560 cm-'. Very strong absorption in addition to the organic ligand bands is observed in the region of 980 and 920 cm-' and assigned to the V = O and 0-0 stretchings, r e s p e c t i ~ e l y . ~ ~ ' ~ Only a few well-refined X-ray structure analyses of peroxovanadates were rep0rted.'9~~'~ The vanadium is seven-coordinated in all but one," which is described as a distorted pentagonal pyramid. The distorted pentagonal bipyramid used as model in the other four structures invariably shows V=O on an apical position and the peroxo group(s) in the equatorial planes. Such seven-coordination is also common in peroxo complexes of Mo(VI)21and Ti(IV),22while Nb(V) prefers eight-coordinated dodecahedral s t r u c t ~ r e s . The ~ ~ complexes are usually monomeric, and a few dimeric ones e x i ~ t . ' ~The . ~ ~coordination of the peroxo group, the 0-0distance, and the MOO bond angles depend upon the metal ion, the symmetry of the ligand field, and the heteroligand. With only little sufficiently precise structural data available, some common trends expected within the family of the peroxometal coplexes cannot be detected. More accurate structure determinations of these compounds are needed, and we therefore looked for conditions to prepare crystals of M[VO(02)IDA] adequate for X-ray structure analysis. The potassium salt precipitated invariably in small irregular crystal clusters. Acceptable crystals were obtained of NH,[VO(O,)IDA], and we now report the structure of this compound, which represents the first polymeric structure of a transition-metal peroxo heteroligand complex. X-ray diffraction data were collected on a crystal grown from aqueous solution^^^ and the structure was solved by standard
(11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24)
Okazaki, K.; Saito, K. Bull. Chem. SOC.Jpn. 1982, 55, 785. Orhanovic, M.; Wilkins, R.G. J. Am. Chem. SOC.1967, 89, 278. Djordjevic, C. Chem. Br. 1982, 18, 554. Nakamoto, K.; Morimoto, Y.; Martell, A. E. J . Am. Chem. SOC.1962, 84, 2081. Griffith, K. P.; Wickins, T. D. J . Chem. SOC.A 1968, 397. Svensson, I.-B.; Stomberg, R.Acta Chem. Scand. 1971, 25, 898. Drew, R. E.; Einstein, F. W. B. Inorg. Chem. 1972, 1 1 , 1079. Drew, R. E.;Einstein, F. W. B. Inorg. Chem. 1973, 12, 829. Begin, D.; Einstein, F. W. B.; Field, Y. Inorg. Chem. 1975, 14, 1785. Campbell, N. J.; Capparelli, M. V.; Griffith, W. P.; Skapski, A. C. Inorg. Chim. Acta 1983, 77, L215. Stiefel, E. I. Prog. Inorg. Chem. 1977, 22, 1. Mimoun, H.; Postel, M.; Casabianca, F.; Fischer, J.; Mitshler, A. Inorg. Chem. 1982, 21, 1301. Mathern, G.; Weiss, R.Acta Crystallogr.,Sect. B: Stmct. Ctystallogr. Cryst. Chem. 1971,827, 1572, 1582. Djordjevic, C.; Sinn, E. XXIII International Conference on Coordination Chemistry, Boulder, CO, 1984; p 249.
0 1985 American Chemical Society
